CHAPTER 6:
CHAPTER 6:
CHAPTER 6: GENERAL CONCLUSIONGENERAL CONCLUSIONGENERAL CONCLUSIONGENERAL CONCLUSION
The work described in this thesis investigated new procedures that could beused to synthesise melanin in a reproducible fashion and to test the
effectiveness of sunscreens containing melanin or other sunscreen agents and
characterise skin colour by diffuse reflectance.
Synthesis of melanins Synthesis of melanins Synthesis of melanins Synthesis of melanins
Despite a large number of studies incorporating synthetic melanins, relatively
few studies have examined melanin synthesis techniques as a means of
synthesising melanin reproducibly.
With the method of melanin synthesis outlined in this study melanins were
synthesised in batches. As melanins were synthesised in batches synthesis
variables, such as reaction temperature, condenser water temperature, room
temperature and ambient light, between the batches were minimised.
The synthesis procedure outlined was simple and inexpensive and the
variables were easily monitored and controlled. The method also allowed for
the synthesis of multiple batches of melanin simultaneously in a reproducible
fashion.
Characterisation of melanins Characterisation of melanins Characterisation of melanins Characterisation of melanins
Conversion of the melanin pyrograms to “pseudo-mass spectra” allowed the
objective comparison of melanin batches using software commercially
available for the comparison of mass spectra.
From the results of this study, melanins produced from different precursors
could be differentiated the basis of statistically significant differences in their
pyrograms. Conversely, statistically significant differences between
pyrograms of different batches of melanins produced under the same
conditions from the same precursors could not be demonstrated. The
analytical technique in this study could be used in combination with other
analytical techniques to determine if the melanins synthesised by the methods
outlined in this thesis were reproducible or as the basis of future studies
examining differences between melanins synthesised from the same precursor
but under different conditions.
Characterisation of skin colour by di Characterisation of skin colour by di Characterisation of skin colour by di
Characterisation of skin colour by diffuse reflectanceffuse reflectanceffuse reflectanceffuse reflectance
This section of work was undertaken to provide a method for assessing the
ability of sunscreen formulations to adhere to the skin. As a melanin
containing sunscreen is likely to be brown, the ability of a formulation to
adhere to skin could be monitored by objectively measuring changes in the
skin colour as the product was washed or worn off the skin.
A spectrophotometer was modified to measure diffuse reflectance outside of
the sample compartment. The modifications to the spectrophotometer
spectrophotometers, relatively inexpensive, reliable, and which could
accurately quantify changes in the colour of human skin
This device developed compares favourably with similar devices described in
the literature in terms of reproducibility and has the advantages of shorter
scan times and a higher resolution. It was simple to construct and at about
A$600 was approximately one tenth the cost of similar commercial devices.
In vitro In vitro In vitro
In vitro evaluati evaluati evaluati evaluations of Sun Protective Factors of sunscreen agentons of Sun Protective Factors of sunscreen agentons of Sun Protective Factors of sunscreen agentons of Sun Protective Factors of sunscreen agent
In vivo methods are the accepted method for the determination of SPF values of sunscreens. However, in vivo methods for determination of the SPF values of sunscreens formulations are time consuming and expensive. In vitro
methods have the potential to give rapid results at a fraction of the cost of
in vivo methods. Unfortunately, in vitro methods often correlate poorly with
in vivo results and are generally unable to determine high SPF values accurately due to limitations in the ability of in vitro methods to measure a wide range of light levels.
The in vitro study presented here used human stratum corneum and Transpore surgical tape as substrates, which were easily obtained. The
in vitro method was fast, simple and capable of measuring high SPF
sunscreens (>70). Although more data in the high SPF range (>30) would be
required to confirm results in this range. The value of this technique was
in vivo testing. The corrected value was subsequently confirmed by independent in vivo testing.
Few naturally occurring pigments command more widespread interest than
melanins [22]. As the development of novel pharmaceutical products
containing melanin increases, methods for the synthesis and characterisation
of melanin containing products will become increasingly important.
Furthermore, there is currently a high consumer demand for sunscreen
products that offer better protection from sun damage, due in part to public
education campaigns and the increased understanding of the mechanisms
and long term effects of sun exposure. The development of fast, inexpensive
and reliable techniques for ascertaining the efficacy of sunscreens will hasten